A patient suffering from a chronic disease such as a cardiac disease should monitor his/her health state, and for this, the patient should directly visit a hospital inconveniently with great costs.
In case of existing sensors, accuracy of heart activity signal measurement deteriorates if a contact point between an electrode and a human body deviates due to a motion of a user. In addition, such existing sensors are inconvenient since they should be mounted to excessively press a human body for a long time. These sensors are not suitable for continuous measurement at daily life.
Korean Patent Registration No. 10-0863064 or the like proposes a bio-signal measurement clothing to which an electrode is mounted. This clothing includes at least one electrode integrally coupled to the inner side of the clothing and coming into contact with the skin surface to detect a bio signal. However, if a human body moves while the electrode integrated with the clothing is detecting a bio signal in contact with the human body, a signal with much motion artifact is detected, which deteriorates accuracy and precision in analysis of the detected bio signal. In other words, even though bio signal may be detected non-restrictively, non-Invasively and continuously by using the existing clothing integrated with an electrode, since a gap is inevitably present between the electrode and the human body due to bent portions of the human body, if the human body moves, the electrode moves accordingly and thus the motion artifact increases as much due to the gap.
Therefore, there is needed clothing with a minimized motion artifact to which a textile electrode kit is mounted, which may measure a bio signal through clothing in a non-restrictive, non-invasive and continuous way anytime and anywhere while minimizing a measurement artifact caused by a motion of the user.
In the textile electrode kit of the present disclosure, a non-contact electrode as well as a contact-type electrode, which has been widely used in the art from the past, is used.
In the present disclosure, as a non-contact electrode, a coil-type magnetic induction sensor is used. In relation to the coil-type magnetic induction sensor, the inventors of the present disclosure have a patent right for Korean Patent Registration No. 10-1302600 which is directed to a conductive textile-based bio signal measurement sensor.
FIG. 1 is a diagram for illustrating a configuration for detecting a volume change according to a change of inductance by using the conductive textile-based bio-signal measurement sensor disclosed in Korean Patent Registration No. 10-1302600.
An inductor-type bio-signal measurement sensor 40 is mounted, and a signal detector 30 is mounted to an outer side of the inductor-type bio-signal measurement sensor. The detector includes an oscillating unit 50 and a demodulating unit 70.
The oscillating unit 50 is composed of an oscillation circuit having L and C to transmit a vibration signal to the inductor-type bio-signal measurement sensor 40.
The inductor-type bio-signal measurement sensor 40 is configured to maximize sensitivity by disposing a ferromagnetic substance core capable of focusing a magnetic flux on a center portion of the coil. In other words, a volume of interest (VOI) may cause a temporal variation, formed by a geometric structure of a coil sensor, namely influenced by a magnetic force, and the conductive textile-based bio-signal measurement sensor 40 senses a change of eddy current caused by electric conductivity of a substance located in the volume.
If the inductor-type bio-signal measurement sensor 40 receives a vibration signal, a magnetic field of a time-varying function is formed in a living body in the volume of interest (VOI) 20, and the generated magnetic field creates an eddy current in the substance. The inductance of the sensor is influenced by a movement of a detection target. Therefore, a vibration signal of the heart muscle causes a change of inductance of the coil, and this signal is transmitted through the oscillating unit 50 to the demodulating unit 70.
The demodulating unit 70 removes a vibration signal applied to the inductor-type bio signal measurement sensor 40 from the above signal to detect only a bio signal.
In detail, a magnetic field is formed by a current minutely flowing on the coil of the inductor-type bio-signal measurement sensor 40. The magnetic field varying according to time induces an eddy current in a detection target (or, in a human body), and the formed induced current generates a minute magnetic field in a direction opposite to the magnetic field formed at the coil. The change of the magnetic field of the coil of the inductor-type bio-signal measurement sensor 40 results in a variation of the inductance (the induced magnetic field) of the coil. To detect the variation, the oscillating unit 50 serving as an oscillation circuit is provided to regard the coil of the inductor-type bio-signal measurement sensor 40 as an inductor circuit, and in this case, a frequency modulation representing a variation of a frequency of an oscillator exhibited due to a movement of a detection target (in a human body). As one of detection methods, the demodulating unit 70 may trace a modulated frequency by using a phase-locked loop (PLL). If this frequency demodulation is used, a movement of the detection target is exhibited as a PLL output, which allows a movement of the heart to be measured.